Evolution: Did recognition of evolution as a natural process begin with Origin of the Species?

1
Evolution Did recognition of evolution as a
natural process begin with Origin of the Species?

• Nope

2
Evolution was discussed and debated for over 100
years before Darwin published his work

• These discussions helped lay the foundation for
  Darwins Theory of Evolution by Natural Selection

3
Changes in Scientific Thought Through Observation
and Investigation

• Judeo-Christian culture - species were
  individually designed and permanent
• Natural Theology 1700s, discover the Creators
  plan by studying nature
• Natural Theology was based on the body of
  knowledge available at that time

4
Carolus Linnaeus and Taxonomy

• Reveal steps of life fashioned by the Creator
• Science of taxonomy came of this
• Linnaeus classification system was important to
  Darwins work
• System is still in use today

5
Fossils and Cuvier

• Relics or impressions of remains of organisms
• Intense study of fossils began in 1700s
  (paleontology)
• Found in sedimentary rock, revealed by erosion

Paleontology refined as a science by Georges
Cuvier (1769-1832)
6
Fossils and Cuvier

• Cuvier recognized fossils deposited in layers
  (strata)
• Observed that species disappeared and new ones
  appeared in different strata
• Disagreed with evolutionists of his time

7
Catastrophism

• Cuvier proposed that each boundary between strata
  corresponded to some catastrophic event
• Event destroyed many of the taxa present at time
• Event was localized
• New species came from unaffected areas

8
Catastrophism

• Cuviers worked in a limited geographic area
• Later discoveries of similar strata in other
  areas revuted Cuviers theory

9
Gradualism

• James Hutton (1726-1797) proposed a theory that
  contrasted with Cuviers
• Gradualism
• Geological formations are the product of slow but
  continuous processes
• Influential in the understanding of evolution

10
Uniformitarianism

• Charles Lyell (1797-1875)
• Incorporated gradualism into his theory of
  uniformitarianism
• Rate at which geological processes occur has
  stayed the same throughout Earths history
• These rates meant Earth had to be older than
  6,000 years

11
Lamark An Evolutionary Theory

• Jean Baptiste Lamark (1744-1829)
• Proposed the first comprehensive model of how
  life evolves
• Published in 1809 (year Darwin was born)
• Lamark studied invertebrates
• Lineages from fossils to living species

12
Lamark An Evolutionary Theory

• Perceived evolution as an organisms attempt to
  achieve perfection
• Innate tendency toward greater complexity
• Equated increased complexity with perfection
• As organisms attained perfection, they were
  better adapted for the environment

13
Basis of Lamarks Model

• Lamark based model on two popular ideas of his
  time
• Use and Disuse
• Inheritance

14
Use and Disuse

• Continued reliance on one or more characteristics
  would make that/those characteristics better
  adapted
• Disuse would cause a feature to be lost
• Acquired adaptations from use would be passed to
  next generation
• Example - Blacksmith

15
Inheritance

• Lamark was describing the inheritance of acquired
  traits
• Acquired traits are features developed by an
  individual and are not genetic therefore, cannot
  be inherited

16
Ridicule of Lamark

• Evolution was not widely accepted in the
  scientific community
• Ridiculed by Cuvier
• Ridicule today based on Cuviers comments
• Lacked supporting data

17
Lamarks Contribution

• Use and disuse
• Adaptation to the environment
• Inheritance

18
The Darwinian Revolution

• Darwin studied for the clergy (most scientists
  and naturalists did)
• Most ships travelling to distant lands carried a
  naturalist
• Darwin joined HMS Beagle as naturalist on a trip
  around the world
• Assignment was to collect, plant, animal and
  fossil specimens

19
(No Transcript)
20
Darwin Focused on Adaptation After Returning

• Fossils and living plants and animals of South
  America and Australia were unique to those
  regions
• Galapagos Islands
• geologically young islands
• apparent differences in flora and fauna of each
  of the islands
• differences among similar plants and animals on
  same island

21
Darwin Focused on Adaptation After Returning

• Organisms appeared to differ in response to the
  conditions of their environment

22
Main Points of The Origin of Species

• Biological diversity is the product of evolution
• Descent with modification
• Tree of Life and Linnaeus classification
  system
• Natural selection as a mechanism through which
  evolution proceeds

23
Process of Developing His Theory

• Observation 1 - Species have the ability to
  produce an excess number of young
• Observation 2 - Populations tend to remain
  stable in size
• Observation 3 - Resources are limited in
  availability

24
Process of Developing His Theory

• Observation 1 - Species have the ability to
  produce an excess number of young
• Observation 2 - Populations tend to remain
  stable in size
• Observation 3 - Resources are limited in
  availability
• Inference 1 - Production of more individuals
  than can be supported leads to a struggle for
  existence, with only some of offspring surviving

25
Process of Developing His Theory

• Observation 4 - Individuals in a population vary
  extensively in their characteristics
• Observation 5 - Much of this variation is
  heritable

26
Process of Developing His Theory

• Observation 4 - Individuals in a population vary
  extensively in their characteristics
• Observation 5 - Much of this variation is
  heritable
• Inference 2 - Survival in struggle for existence
  is not random. Individuals with characteristics
  that improve chance for survival are the most
  fit.
• Inference 3 - Differences in probability to
  survive will lead to change in a population

27
What does natural selection mean to us?

• Changes in the makeup of a population in response
  to fluctuating environmental conditions
• Loss and gain of species

28
Reception for Darwins Theory During His Time

• Most biologists were convinced about evolution
• Natural selection not widely accepted
• Why?

29
Basic Tenet of Natural Selection

• The most fit organisms (survivors) will reproduce
  and pass their genes on to the next generation.

Problem Process of inheritance not understood
30
Gregor Mendel

• Presented his work in 1865
• Was largely ignored, in fact ridiculed
• Was rediscovered in early 20th century

31
Marriage of Mendel and Darwin

• Early interpretation of Mendels work did not
  provide support for natural selection
• Either/or traits
• Natural selection requires variation in traits
• Later recognized variation does exist (population
  genetics)

32
Modern Synthesis

• Developed in 1940s
• Integrated natural selection and genetics
• Integration of several disciplines
• paleontology (Simpson)
• taxonomy (Mayr)
• genetics (Dobzhansky)

33
Modern Synthesis

• Evolution occurs at level of population, not the
  individual
• A population has a gene pool, with some frequency
  of occurrence for the alleles that express
  respective traits
• Evolution produces changes in the allele
  frequencies of a population

34
Main Points of Exercise

• Darwin - mechanism for evolution, not evolution
  itself
• Evolution idea present before Darwin
• Body of Knowledge
• Scientific Scrutiny/Skepticism